Ajax <select> boxes?

Another newbie question, I guess… Does anybody have a good pointer on
where to find information about Ajax in ruby? I already did the ONLamp
tutorial on the subject and I can do some minor things with it, but what
I really like to do is change the values in a second select box, using
data gathered from the database according to the value in the first
select box.

User selects a city, the second select box shows rent prices that that
city has rooms for rent in…

thanks in advance,

danny

actually never mind, just found it using the API docs…